The general conditions for the catalytic hydroreforming reactions are as follows: the average temperature of the reactor or reaction zone ranges from about 480.degree. to 600.degree. C., the pressure is in the range from 5 to 20 kg/cm.sup.2, the hourly velocity ranges from 0.5 to 10 volumes of liquid naphtha per volume of catalyst and the recycling rate from 1 to 10 moles of hydrogen per mole of charge. The charge may be a naphtha distilling between about 60.degree. C. and about 220.degree. C., particularly a straight-run naphtha. The catalyst contains, for example, at least one noble metal from the platinum family, i.e. a noble metal such as platinum, palladium, iridium, ruthenium or osmium, deposited on a carrier of alumina or an equivalent compound. The total content of noble metals is from 0.1 to 2.0 % by weight in proportion to the catalyst and the halogen (preferably chlorine or fluorine) content is from 0.1 to 10% by weight. Other types of carriers, such as amorphous or crystallized silica-aluminas, silica-magnesias, silica-thorias, alumina-magnesias etc . . . , can be used.
The catalyst may contain at least one other metal promoter selected from various groups of the periodic classification of elements.
The general conditions for reactions producing aromatic hydrocarbons from saturated or unsaturated gasolines (process of "Aromizing" type or similar) are for example as follows:
When the charge is unsaturated, i.e. when it contains diolefins and monoolefins, it must be first freed therefrom by selective or complete hydrogenation. Then, the charge, optionally freed by hydrogenation from substantially all the diolefines and monoolefins contained therein, if any, is subjected, in each reaction zone, to a hydrogen treatment, in the presence of a catalyst comprising a carrier, 0.1 to 10% by weight of halogen and at least one group VIII noble metal (of the platinum family) and also optionally at least one other conveniently selected metal promoter. The content of metals of the platinum family is generally from 0.005 to 5% by weight. The carrier is selected from aluminas and chlorinated and/or fluorinated aluminas, or other similar compounds comprising silica-aluminas, silica-magnesias, silica-thorias, alumina-magnesias, etc . . . . The reaction is conducted at a temperature from about 500.degree. to 600.degree. C., under a pressure from 1 to 60 kg/cm.sup.2, the hourly volume flow rate of the liquid charge being of about 0.1-10 times the catalyst volume and the hydrogen/hydrocarbons molar ratio being of about 0.5-20.
The general conditions for dehydrogenating naphthenic and paraffinic saturated hydrocarbons (having 3-40 carbon atoms per molecule), are as follows: These reactions are performed in the presence of catalysts of the same type as reforming catalysts, at a temperature usually from 300.degree. to 600.degree. C., under a pressure ranging from 0.1 to 30 volumes of liquid charge per volume of catalyst. The hydrogen/hydrocarbons molar ratio at the reactor input is usually from 0.1 to 30.
For the isomerization of alkyl-aromatic compounds and more particularly for the isomerization of C.sub.8 alkyl aromatic hydrocarbons (i.e. xylenes, ethyl benzene and mixtures thereof of composition not corresponding to the thermodynamic equilibrium, and specially mixtures whose paraxylene content is lower than that existing at said equilibrium), the conditions are as follows:
The catalyst comprises, in addition to a conventional carrier at least one metal element having a hydrogenating-dehydrogenating activity for converting ethyl-benzene and also for reducing the catalyst clogging due to the formation and deposition onto the solid of heavy products resulting from a still possible parasitic polymerization.
The one or more metal elements having a hydrogenating-dehydrogenating activity will be particularly selected from group VIII noble metals, i.e. the noble metals of the platinum family, with the optional addition of metals or derivatives of metals from group VI-A (chromium, molybdenum, tungsten) of the periodic classification of elements.
The amount of metal element, or of each metal element when several metal elements are involved, generally ranges from 0.005 to 1% of the catalyst weight.
The reaction will be conducted at a temperature from about 350.degree. C. to 500.degree. C., a pressure from about 5 to 30 bars, a space velocity from about 0.5 to 10 volumes of liquid charge per catalyst volume and per hour and a hydrogen/hydrocarbons ratio ranging from about 2 to 10 (by moles).
The catalyst to be regenerated, which generally contains 0.005 to 5% of at least one noble metal of the platinum family and 0.1-10% of halogen, for example chlorine, is supplied either from a reservoir where it has been stored before being subjected to regeneration or directly from the reactor where the reaction was performed. This catalyst, for example as particles, may be shaped as spheric balls of a diameter generally ranging from 1 to 3 mm, preferably from 1.5 to 2 mm, these values being not limitative. The bulk density of the catalyst is usually from 0.4 to 1, preferably from 0.5 to 9, more particularly from 0.55 to 0.8, these values being not limitative.
The catalyst regeneration is performed in an enclosure where the catalyst is treated as fixed or moving bed. In said enclosure the catalyst is successively subjected, for example, to:
(a) a combustion by means of a molecular oxygen-containing gas,
(b) a simultaneous chlorination or oxychlorination by means of a molecular oxygen-containing gas and of halogen (e.g. chlorine) or halogenated compound, for example a hydracid or alkyl halide, or a halogen halogenated compound mixture.
(c) a final treatment with a gas containing a high proportion of molecular oxygen.
The regeneration may be performed in a regeneration zone wherein the catalyst to be regenerated is arranged in a fixed bed. The catalyst is then regenerated in the fixed bed in three successive steps (a), (b) and (c) successively performed on the fixed catalyst bed.
Detailed conditions for the regeneration process are preferably as follows:
(a) the first step corresponds to the combustion of the coke deposits. This operation is performed by introducing air in an inert mixture (formed for example of nitrogen and carbon dioxide), this inert mixture being used as thermal diluent. The oxygen content of the regeneration gas supplied is preferably from 0.01 to 1% by volume. The air supplied is consumed by combustion of the coke deposits and the end of the combustion is easily detected by the increase of the oxygen content of the gas flowing out from the regenerator and also by the disappearance of the flame front (the horizontal plane where the combustion occurs) which propagates downwardly through the catalyst bed. The combustion is achieved at an average temperature ranging preferably from 350.degree. to 550.degree. C., under a pressure of, for example, 1-15 kg/cm.sup.2.
The combustion temperature is adjusted by controlling the oxygen concentration, the gas temperature at the regenerator input, as well as the gas velocity, so as to maintain the temperature at the level of the flame front, which is lower than that corresponding to the beginning of roasting, generally below 700.degree. C., preferably of about 450.degree. C. This gas flow is maintained for a sufficient time to remove coke from the catalyst. Accordingly, substantially all the coke can be removed by this way.
Generally, the amount of coke remaining on the catalyst may be reduced to about 0.5% by weight in 4 hours of regeneration and to less than 0.1% in 6 hours.
(b) The second step corresponds to the catalyst chlorination or oxyhalogenation. For oxyhalogenation, the oxygen content of the regeneration gas supplied to the regenerator is increased up to a value from 1 to 8% by volume, by simultaneously introducing a compound containing a halogen (chlorine or fluorine), i.e. either a halogen (mainly chlorine or fluorine) or a hydracid (e.g. HCl, HF or HBr) or an alkyl halide containing 1-6 carbon atoms per molecule, for example chloroform, tert-butyl chloride, cyclohexyl chloride, isopropyl fluoride, tert-butyl fluoride, cyclohexyl fluoride, dichlorodifluoromethane or preferably carbon tetrachloride. The alkyl halide is used in an amount sufficient to form an alumina halogenated derivative in a proportion of 0.5-1.2% by weight of the catalyst subjected to regeneration. Mixtures of halogenated compounds, for example a mixture of chlorine and hydrochloric acid containing about 5-60% of hydrochloric acid and 95-40% of carbon tetrachloride, can also be used. Other halogenated compounds such for example as thionyl chloride or nitrosyl chloride, ammonium chloride or fluoride, halogenated organic acids such as monochloroacetic and trichloracetic acids, or any other equivalent compound may also be used.
The chlorination or oxyhalogenation is conducted at an average temperature from 350.degree. to 550.degree. C. under a pressure from about 1 to 15 kg/cm.sup.2. This treatment lasts for example from 20 mn to 3 hours, generally about 1 hour.
(c) The third final regeneration step corresponds to the oxidation of the catalyst. It is performed by further increasing the oxygen content of the regeneration gas supplied to the regenerator up to a value from 3 to 20% by volume and then maintaining the regenerator at an average temperature from 350.degree. to 550.degree. C. under an average pressure from 1 to 15 kg/cm.sup.2. This operation lasts for example from 30 mn to 6 hours, preferably from 40 minutes to 2 hours. It is generally about 2 hours.
After the third step, the regenerator is usually purged with nitrogen, then filled with hydrogen in pressure equilibrium with the the reaction zone where the catalyst will be introduced. The catalyst is then stored or immediately transferred from the regenerator to a reactor through a suitable valve system. But, before being introduced into a reactor, or at the top therof, the catalyst is generally first treated with a hydrogen stream at a temperature for example of 300.degree.-550.degree. C. and under a pressure for example 3 to 25 kg/cm.sup.2, preferably from 5 to 20 kg/cm.sup.2. The catalyst sulfurization, when necessary, will be performed in said space or at the top of the reactor itself or in various lines for transferring the catalyst to the top of said reactor.